The VA-based AIDS Network (VA Net) is a multicenter clinical trials organization established to study the long-term effectiveness of HIV therapies and to develop medical management strategies to treat HIV infection, as a chronic disease. In 1999, 13 drugs are available to treat HIV infection and people with HIV are living longer. HIV can no longer be considered a uniformly rapidly fatal, acute disease. The approach to research on HIV as a chronic disease is different than previous HIV research that has predominantly been focused on development of new HIV drugs and understanding of HIV pathogenesis. VA Net will conduct research to learn how to use the drugs that are available to develop evidence-based strategies to manage HIV as a chronic disease. To do this type of research, large and long-term trials of the effectiveness of differing medical management strategies will be initiated by VA Net. This requires a research network capable of enrolling large number of patients where long-term follow-up is easy. VA Net was formed in 1998 by the partnership of major national comprehensive health systems and independent medical centers experienced in HIV care and research. Under VA Net, the single provider of HIV care in the U.S., the Department of Veterans Affairs, has joined with regional groups of the Kaiser-Permanente Healthcare system and other independent medical centers. VA Net member groups provide medical care to nearly 35,000 persons with HIV infection; over 10 percent of those in care in the U.S. VA Net has three operational components; the VA Net clinical sites, described above; the VA Net Statistical and Data Management Center (SDMC); and the VA Net Coordinating and Research Operations Center (CORC). The SDMC is co-located with the VA Cooperative Studies Program Coordinating Center in West Haven, CT. The SDMC has many years of experience in the conduct of effectiveness and long-term strategy research in other areas of medicine and will now apply that experience to HIV. The CORC is a project of the Center for Health Information Management in Bethesda, MD, and provides all organizational, operational and administrative support for VA Net activities. There are 34 VA Net clinical sites in Year 1 with a planned expansion in Year 2 to include 45 sites. VA Net expects to initiate seven studies in its inaugural year; two full protocols (total enrollment of 9000) and five laboratory based substudies (total enrollment 8,800) and plans to initiate an additional five protocols and one laboratory substudy in Year 2. VA Net is managed by a Principal Investigator and Associate PI who lead an Executive Committee and a Science Committee, the latter of which initiates and directs the research agenda of VA Net.